Submerged twin wire paper former

ABSTRACT

A TWIN WIRE PAPER WEB FORMING MACHINE WHEREIN THE WIRES ARE GUIDED INTO A FORMING THROAT OVER BREAST ROLLS AND THEN INTO A FORMING RUN WITH THE SLICE OPENING DELIVERING A STOCK JET INTO THE THROAT AND A CONTAINER CONTAINING WHITE WATER ON BOTH SIDES OF THE STOCK JET SO AS TO SUBMERGE IT AND MAINTAIN WATER ON THE OFFRUNNING SIDE OF THE BREAST ROOLS. THE BASIS WEIGHT PROFILE CAN BE CONTROLLED BY ADDING TO OR INTERFERING WITH THE STOCK JET BEFORE IT ENTERS THE THROAT. THIS IS ACCOMPLISHED BY EMPLOYING AN ADDITIONAL STOCK JET OR PLACING ADJUSTABLE BAFFLES IN A POSITION TO BLOCK A PORTION OF THE JET AND REDUCE ITS THICKNESS.

Aug. 27, 1914 J. D. PARKER SUBMERGED TWIN WIRE PAPER FORIBR Filed Oct. 6, 1971 INVENTOR. V J0SEP D, I A

BY I V TTOR EYS United States Patent US. Cl. 162-203 Claims ABSTRACT OF THE DISCLOSURE A twin wire paper web forming machine wherein the wires are guided into a forming throat over breast rolls and then into a forming run with the slice opening delivering a stock jet into the throat and a container containing white water on both sides of the stock jet so as to submerge it and maintain water on the offrunning side of the breast rolls. The basis weight profile can be controlled by adding to or interfering with the stock jet before it enters the throat. This is accomplished by employing an additional stock jet or placing adjustable bafiles in a position to block a portion of the jet and reduce its thickness.

BACKGROUND OF THE INVENTION The invention relates to an improved structure and means for forming a web of paper between parallel converging dewatering wires and particularly to improvements in the relationship of structures which deliver a jet of stock to a tapered forming throat between the wires which avoid the problems of high-speed formation that are associated with free surfaces, entrainment of air, roughness of the free jet and spray or splash.

It has heretofore been contemplated to supply a plurality of liquids to fill a throat to form a web or to fill the interstices of a forming wire with water before the web is formed, but the problems of a high-speed jet entering the throat between a pair of forming wires have not been fully solved. The present invention provides a structure and method wherein the nip between the forming wires and the discharge from the headbox is completely submerged. This arrangement provides for the total exclusion of air from the initial drainage zone. The concept includes completely protecting and submerging the jet of stock which emerges from a slice opening until it enters the forming throat between forming wires and to completely submerge the nip between the forming wires and to further submerge the otirunning side of the breast rolls carrying the forming wires. This insures the absence of any free surface of the discharge jet emerging from the slice opening. An advantage of submerging the initial area of a twin wire forming system is that the problems associated with free surfaces, entrainment of air, roughness of the free jet, spray or splash, are avoided. Also, the arrangement eliminates the need for complicated sealing devices between the headbox and twin wire nip so that more conventional discharge nozzles and forming nip configurations can be used. Further, no stationary devices need contact the wires of the rolls. With the exclusion of air from around the discharge jet, extremely high levels of turbulence can be used without having to close couple the headbox slice in the nip between the wires and without the problems of air entrainment. This eliminates formation defects due to air bubbles drawn into the forming zone. In one form it is contemplated to operate with anexcess delivery and a large degree of back flow or rejection of the discharge jet in the forming nip. This will permit the headbox nozzle to be rigid and nonadjustable. Also, the clearance between the breast rolls may then be adjusted to determine the basis weight of the formed sheet.

3 ,832,282 Patented Aug. 27, 1974 In another arrangement it is contemplated to utilize the principles of the invention and further make cross-machine basis weight profile adjustments by creating localiz/ed disturbances in the surfaces of the submerged jet with small jets, battles, or probes. It is also possible that the submerging chamber which contains the protective liquid for the jet can serve as the white water chest.

It is accordingly an object of the present invention to provide an improved twin wire forming machine with a stock jet having relative high turbulence introduced into therthroat and protecting the jet from air entrainment to improve the formation of the web between the wires.

A further object of the invention is to provide an improved twin wire forming mechanism with improvements at the forming throat portion of the machine which avoids difi'iculties heretofore encountered and improves the formation of a paper web.

Various other objects and advantages, and other embodiments will become apparent to those versed in the art within the scope of concepts of the invention as it is described and disclosed in the claims, specification and drawings, in which:

' IN THE DMWINGS FIG. 1 is a schematic end elevational view of a forming section of a paper machine constructed and Operating in accordance with the principles of the present invention;

FIG. 2 is a schematic fragmentary side elevational view showing one end of the mechanism of FIG. 1; and

FIG. 3 is a fragmentary end elevational view of another form of operation of the mechanism of the invention.

DESCRIPTION As shown in FIG. 1, a pair of traveling looped forming wires 10 and 11 are arranged to provide a web forming run between them. The looped wires have within them opposed breast rolls 12 and 13 training the wires to provide a tapered forming throat 14. The wires are tensioned over a plurality of support means 16 which extend across the wires and are generally arranged in a curved path but are spaced so that the wires travel over a series of chords between them. The formation of a web from fiber stock begins in the forming throat 14 and the water carrier of the stock is gradually expressed through the porous forming wires 10 and 11 as the wires travel in their converging paths. Additional skimmer-s 17 aid in removing water from the wire 10. Further removal of the water is aided by a suction box 19, and the wire 11 after the suction box 19 passes over a couch roll 20 with a suction gland therein. The web follows the wire 11 to a pick-up roll 22. The other wire 10 passes upwardly over a couch roll 21 over which it turns and additional supporting rolls are provide'd within each of the wires for tensioning them and permitting them to return to the breast rolls 12 and 13.

Stock is delivered in a jet 25 from a headbox 23 having a slice opening 24. The stock jet 25 emerges from the opening 24 at a relatively high velocity which is substantially at the velocity of the traveling wires 10 and 11. While the structure could operate in other positions, a vertical delivery of the stock jet 25 is preferred. A horizontal arrangement is possible by training the wire web sandwich over a roll before exit from the liquid.

The liquid within the tank protects and confines the open stream of stock 25 emerging from the slice opening 24. This prevents air entrainment and free surface disturbances of the stock within the jet 25 during the time it is traveling from the slice opening to the forming throat 14. The water in the submerging tank 26 also preferably is of a depth so that it covers the breast rolls on the offrunning side in the area 28. An important reason for submergence of the rolls is to minimize entrainment of air through a free surface by moving parts. By submerging the rolls, you have to contend only with wires on the return run entering the free surface.

In some structures the jet is confined to a width so that it will pass freely between the breast rolls and will not engage the wires until beyond their point of tangency to the wires to avoid pumping.

The container 26 preferably contains white water and the entry of a certain amount of water with the wires within their interstices performs a sealing function since this water will emerge from the wires back into the container as the wires begin to converge in the throat 14 and begin to squeeze water from the stock. Also, White water extracted from the stock in the throat 14 passes into the container which serves as a receptacle for water expressed from the web.

In one form of structure, as shown in FIG. 3, an excess of stock is delivered to the space between the rolls so that a back flow of stock occurs. The outer layer of stock will flow into the container as back flow and only the inner strata of stock will enter between the breast rolls. In the structure of FIG. 3, wires 30 and 31 are shown supported on breast rolls 33 and 34 to form a forming throat 32. The headbox 35 has a slice opening 36 and the structure is surrounded by an enveloping chamber of liquid 38. The breast rolls have adjusting structure 33a and 34a which permit the adjustment of the positions relative to each other. This adjustment with the supply of a surplus of stock can be used to control the basis weight of the paper formed.

It is also contemplated that with the arrangement of FIGS. 1 or 3, an impingement means or bafile 29 may be provided between the space 28 between the breast rolls and the slice opening 24. These impingement means may be used to block a portion of the jet and reduce the thickness of the stock jet to control the basis weight. The bafile 29 may be adjustable and be flexible or of multi parts and positionable toward or away from the jet along their lengths to control the basis weight across the web which is formed.

Also, the baflle 29 may instead take the form of means for delivering additional stock to supplement the stock of the jet 25 and thereby increase the basis weight of the web. In other words, means may be provided to either interfere with the stock jet or add to it to utilize the structure for controlling web basis weight thereby permitting the use of a rigid nonadjustable slice. Adjustment in the position of the member 29 is by suitable power means 29a shown schematically by the arrowed line 29a.

The container with its sealing liquid extends over the ends of the rolls to seal the ends as shown in FIG. 2.

I claim as my invention:

1. A structure for making a web from a slurry of fiber containing stock comprising in combination:

first and second looped endless foraminous forming wires,

wire guides for said wires forming a nip therebetween guiding said wires together in a tapered forming throat followed by a forming run wherein the wires travel generally parallel with water passing out through the wires and a web being carried between them,

stock dewatering means along said forming run in close running relation with said wires,

a headbox having a slice opening positioned in alignment with said throat delivering a pressure jet of stock to said throat,

and a liquid container enveloping said breast rolls and slice opening having a depth for holding a liquid at a sufficient level for submerging the nip between the wires entering the forming zone and submerging said slice opening and the forming wires in the throat and positioned so that water passing from the stock through the wires along said path may pass into the container,

the forming run being located outside said container to be out of contact with the liquid in the container.

2. A structure for making a web from a slurry of fiber containing stock constructed in accordance with claim 1 wherein said guides which provide said forming throat are rolls, and said rolls are also completely submerged in the liquid in said container.

3. A structure for making a web from a slurry of fiber containing stock constructed in accordance with claim 1 wherein said wires travel upwardly in said throat and said slice opening is oriented such that the jet is projected upwardly into the throat.

4. A structure for making a web from a slurry of fiber containing stock constructed in accordance with claim 1 including means positioned between the slice opening and the throat afiecting the flow stream from the slice opening and being locally adjustable for affecting the crossmachine basis weight profile of the web.

5. A structure for making a web from a slurry of fiber containing stock constructed in accordance with claim 4 wherein said means affecting the flow stream is in the form of a baflle.

6. In a structure for making a web from a slurry of fiber containing stock having first and second looped foraminous forming wires with guides for the wires guiding the wires together in a tapered forming throat followed by a dewatering path wherein the wires travel generally parallel with the web between them and a headbox having a pressure slice opening in alignment with the throat delivering stock to the throat and a liquid container for holding liquid submerging the wires entering the forming zone, the method of operation wherein an excess of stock is delivered to the throat so that a substantial bac-k flow occurs, and the excess water from the back flow is collected in the liquid container.

7. In a structure for making a web from a slurry of fiber containing stock having first and second looped foraminous forming wires with guides for the wires guiding the wires together in a tapered forming throat followed by a dewatering path wherein the wires travel generally parallel with the web between them and a headbox having a pressure slice opening in alignment with the throat delivering stock to the throat and a liquid container for holding the liquid submerging the wires entering the forming zone, the method of operating said structure and affecting the cross machine basis weight profile by interfering with the stock jet after it leaves the slice opening and before it enters the forming throat, and collecting any stock not entering the forming throat in the container.

8. A structure for making a web from a slurry of stock comprising in combination,

first and second looped endless foraminous forming wires,

wire guides for said wires guiding the wires together in a tapered forming throat followed by a forming run wherein the wires travel generally parallel with the web between them,

a headbox having a slice opening delivering a jet of stock to said forming throat,

and a container positioned for containing non-stock containing liquid on each side of the jet and submerging the slice opening and the forming wires in the throat thereby excluding air from entering the forming throat and preventing splash, said forming run being located outside of said container to be out of contact with the liquid in the container.

9. A structure for making a web from a slurry of stock constructed in accordance with claim 8 and including breast rolls within the forming wires guiding the wires into said throat and including Water on the offrunning side of said rolls between the wire and rolls preventing pumping of the stock entering the throat.

10. A structure for making a web from a slurry of fiber containing stock comprising in combination,

wires,

1 5 wire guides for said wires forming a nip therebetween guiding said wires together in a tapered. forming throat foll wed by a forming run wherein the wires travel generally parallel with water passing out through the wires and a web being carried between them,

stock dewaterin-g means along said forming run in close running relation with said wires,

a headbox Having a pressure slice opening positioned in alignrnfnt with said throat for delivering a pressure jet ofif stock directly into said throat,

and a liquid: container having a depth for holding a liquid at? sufficient level for submerging the nip between ,the wires and said pressure jet of stock entering [the forming zone so that the pressure jet emerging? rom the slice opening does not entrain air in entering the throat.

References Cited UNITED s. LEON BASHORE, Primary Examiner R. H. TUSHIN, Assistant Examiner US. Cl. X.R. 

